Jacobs, 29, averaged only 3.8 yards per carry last season. He did score seven rushing touchdowns and eight total touchdowns. He has 17 total touchdowns over the last two seasons.

Jacobs' three longest runs last season -- covering 34, 28 and 19 yards -- came from Week 14 or later, including one against the Atlanta Falcons in the wild-card playoff round. He played on early downs and in short-yardage situations, gaining six first downs on 11 third- or fourth-down rushes when the Giants needed 2 or fewer yards for a first down.

Jacobs is 6-foot-4 and 264 pounds, but less physical as a runner than Gore or any of the leading NFC West backs. His addition would not seem to threaten Kendall Hunter, the 49ers' primary backup and a promising young player, but rather power back Anthony Dixon.

Dixon gained first downs on all three of his short-yardage rushing attempts (defined the same way I defined them for Jacobs earlier in this item). Hunter converted once on five of these rushes. Gore converted eight times in 16 chances, including on the 49ers' only attempt during postseason.